Hadoop run the process in commodity hardware, so it’s possible to fail the SYSTEMS also has low memory. So if system FAILED, process also failed, it’s not recommendable.Speculative execution is a process performance optimization technique.Computation/logic DISTRIBUTE to the multiple systems and execute which system execute quickly. By default this value is true. Now even the system crashed, not a problem, framework CHOOSE logic from other systems. 

Eg: logic distributed on A, B, C, D systems, COMPLETED within a time.

System A, System B, System C, System D systems executed 10 min, 8 mins, 9 mins 12 mins simultaneously. So consider system B and kill remaining system processes, framework take care to kill the other system process. 

Hadoop run the process in commodity hardware, so it’s possible to fail the systems also has low memory. So if system failed, process also failed, it’s not recommendable.Speculative execution is a process performance optimization technique.Computation/logic distribute to the multiple systems and execute which system execute quickly. By default this value is true. Now even the system crashed, not a problem, framework choose logic from other systems. 

Eg: logic distributed on A, B, C, D systems, completed within a time.

System A, System B, System C, System D systems executed 10 min, 8 mins, 9 mins 12 mins simultaneously. So consider system B and kill remaining system processes, framework take care to kill the other system process.